GHSA-JH4V-GFQJ-7RHX

Vulnerability from github – Published: 2026-09-17 14:52 – Updated: 2026-09-17 14:52
VLAI
Summary
RabbitMQ Java client has frame-level OOM: Math.min(maxInboundMessageBodySize, 0) defeats frame size enforcement
Details

Vulnerability

In AMQConnection.java (line 435-436), after Connection.Tune negotiation, the frame-max limit is set via:

_frameHandler.setFrameMax(
    Math.min(this.maxInboundMessageBodySize, frameMax));

When frameMax = 0 (meaning "unlimited" per AMQP spec), Math.min(67108864, 0) = 0. This value is then passed to Utils.framePayloadLimit(0) which returns Integer.MAX_VALUE (line 77-79 of Utils.java):

static int framePayloadLimit(int frameMax) {
    if (frameMax <= 0) {
      return Integer.MAX_VALUE;
    }
    // ...
}

This completely defeats the maxInboundMessageBodySize protection (default 64MB) at the frame level.

Attack Scenario

A malicious AMQP server (or MITM) sends Connection.Tune with frameMax=0:

  1. Client defaults: requestedFrameMax = 0 (ConnectionFactory.DEFAULT_FRAME_MAX, line 82)
  2. negotiatedMaxValue(0, 0) = Math.max(0, 0) = 0 (line 673-676)
  3. Math.min(maxInboundMessageBodySize, 0) = 0 — 64MB cap defeated
  4. framePayloadLimit(0) = Integer.MAX_VALUE — no frame size enforcement
  5. Attacker sends a single frame with frameSize = 0x1FFFFFFF (~500MB)
  6. Frame.readFrom() (line 135) executes new byte[frameSize] — OOM crash

The frame does not need to be a body frame — method frames, header frames, or heartbeat frames with a crafted size field all trigger the allocation before any content-level check fires.

Root Cause

The AMQP spec uses frameMax=0 to mean "unlimited", but Math.min treats it as the integer value zero. The intent of line 435-436 was to take the smaller of the two limits, but when one limit uses 0-means-unlimited semantics, Math.min always selects the zero, disabling the other limit.

Impact

  • Default configuration is vulnerable: Both requestedFrameMax (client) and legitimate servers' frameMax in Tune may be 0
  • Single-frame OOM: One malicious frame triggers up to ~2GB allocation (Integer.MAX_VALUE bytes)
  • Bypasses existing protection: maxInboundMessageBodySize (introduced to cap allocations at 64MB) is entirely defeated at the frame level
  • Different from ValueReader OOM: This is a frame-layer allocation in Frame.readFrom(), not a value-layer allocation in ValueReader.readBytes()

Affected Code

  • AMQConnection.java:435-436 — Math.min with 0-means-unlimited
  • Utils.java:77-79 — framePayloadLimit(0) returns Integer.MAX_VALUE
  • Frame.java:135 — new byte[frameSize] allocation site
  • ConnectionFactory.java:82 — DEFAULT_FRAME_MAX = 0

Suggested Fix

int effectiveFrameMax = (frameMax == 0)
    ? this.maxInboundMessageBodySize
    : Math.min(this.maxInboundMessageBodySize, frameMax);
_frameHandler.setFrameMax(effectiveFrameMax);

This treats frameMax=0 as "use maxInboundMessageBodySize as the cap" instead of "zero".

Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "com.rabbitmq:amqp-client"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.34.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-75516"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-17T14:52:21Z",
    "nvd_published_at": "2026-09-16T19:17:33Z",
    "severity": "HIGH"
  },
  "details": "## Vulnerability\n\nIn `AMQConnection.java` (line 435-436), after `Connection.Tune` negotiation, the frame-max limit is set via:\n\n```java\n_frameHandler.setFrameMax(\n    Math.min(this.maxInboundMessageBodySize, frameMax));\n```\n\nWhen `frameMax = 0` (meaning \"unlimited\" per AMQP spec), `Math.min(67108864, 0) = 0`. This value is then passed to `Utils.framePayloadLimit(0)` which returns `Integer.MAX_VALUE` (line 77-79 of Utils.java):\n\n```java\nstatic int framePayloadLimit(int frameMax) {\n    if (frameMax \u003c= 0) {\n      return Integer.MAX_VALUE;\n    }\n    // ...\n}\n```\n\nThis completely defeats the `maxInboundMessageBodySize` protection (default 64MB) at the frame level.\n\n## Attack Scenario\n\nA malicious AMQP server (or MITM) sends `Connection.Tune` with `frameMax=0`:\n\n1. Client defaults: `requestedFrameMax = 0` (`ConnectionFactory.DEFAULT_FRAME_MAX`, line 82)\n2. `negotiatedMaxValue(0, 0)` = `Math.max(0, 0)` = 0 (line 673-676)\n3. `Math.min(maxInboundMessageBodySize, 0)` = 0 \u2014 **64MB cap defeated**\n4. `framePayloadLimit(0)` = `Integer.MAX_VALUE` \u2014 no frame size enforcement\n5. Attacker sends a single frame with `frameSize = 0x1FFFFFFF` (~500MB)\n6. `Frame.readFrom()` (line 135) executes `new byte[frameSize]` \u2014 **OOM crash**\n\nThe frame does not need to be a body frame \u2014 method frames, header frames, or heartbeat frames with a crafted size field all trigger the allocation before any content-level check fires.\n\n## Root Cause\n\nThe AMQP spec uses `frameMax=0` to mean \"unlimited\", but `Math.min` treats it as the integer value zero. The intent of line 435-436 was to take the smaller of the two limits, but when one limit uses 0-means-unlimited semantics, `Math.min` always selects the zero, disabling the other limit.\n\n## Impact\n\n- **Default configuration is vulnerable**: Both `requestedFrameMax` (client) and legitimate servers\u0027 `frameMax` in Tune may be 0\n- **Single-frame OOM**: One malicious frame triggers up to ~2GB allocation (`Integer.MAX_VALUE` bytes)\n- **Bypasses existing protection**: `maxInboundMessageBodySize` (introduced to cap allocations at 64MB) is entirely defeated at the frame level\n- **Different from ValueReader OOM**: This is a frame-layer allocation in `Frame.readFrom()`, not a value-layer allocation in `ValueReader.readBytes()`\n\n## Affected Code\n\n- `AMQConnection.java:435-436` \u2014 `Math.min` with 0-means-unlimited\n- `Utils.java:77-79` \u2014 `framePayloadLimit(0)` returns `Integer.MAX_VALUE`\n- `Frame.java:135` \u2014 `new byte[frameSize]` allocation site\n- `ConnectionFactory.java:82` \u2014 `DEFAULT_FRAME_MAX = 0`\n\n## Suggested Fix\n\n```java\nint effectiveFrameMax = (frameMax == 0)\n    ? this.maxInboundMessageBodySize\n    : Math.min(this.maxInboundMessageBodySize, frameMax);\n_frameHandler.setFrameMax(effectiveFrameMax);\n```\n\nThis treats `frameMax=0` as \"use maxInboundMessageBodySize as the cap\" instead of \"zero\".",
  "id": "GHSA-jh4v-gfqj-7rhx",
  "modified": "2026-09-17T14:52:21Z",
  "published": "2026-09-17T14:52:21Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/rabbitmq/rabbitmq-java-client/security/advisories/GHSA-jh4v-gfqj-7rhx"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-75516"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rabbitmq/rabbitmq-java-client/pull/2015"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rabbitmq/rabbitmq-java-client/pull/2016"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rabbitmq/rabbitmq-java-client/commit/6d7c2bfe89796ca34d3531098fb59dd657fea39e"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rabbitmq/rabbitmq-java-client/commit/e7f10bf99aee103dd9f64b3e52a725fc9f9d3763"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/rabbitmq/rabbitmq-java-client"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rabbitmq/rabbitmq-java-client/releases/tag/v5.34.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "RabbitMQ Java client has frame-level OOM: Math.min(maxInboundMessageBodySize, 0) defeats frame size enforcement"
}



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